Moderate Weight Loss Before Bariatric Surgery Tied to Lower Postop Mortality

By Lisa Rapaport

May 29, 2020

(Reuters Health) - People who lose even a modest amount of weight prior to bariatric surgery may have a lower risk of dying within 30 days after surgery, a recent study suggests.

Researchers analyzed data on 480,075 patients who had bariatric surgery between 2015 and 2017 at centers participating in the Metabolic and Bariatric Surgery Accreditation and Quality Improvement Program, which covers 90% of bariatric surgery programs in the U.S. and Canada. Overall, 511 patients (0.1%) died within 30 days.

Mean percentage of weight loss prior to surgery was 4.0%.

After adjusting for age, sex, race, type of surgery, smoking status, and co-morbidities, researchers found that compared with patients without weight loss before surgery, those who lost up to 4.9% of their body weight were 24% less likely to die in the 30 days after surgery (odds ratio 0.76).

Greater weight loss was associated with even lower postoperative mortality risk, with odds ratios of 0.69 and 0.58, respectively, for patients who lost 5% to 9.9% of their weight and for patients who lost at least 10% of their weight.

"The take-home message is that weight loss, even modest weight loss, prior to bariatric surgery matters," said senior study author Dr. Wei Bao, an assistant professor of epidemiology in the College of Public Health at the University of Iowa in Iowa City.

"Weight loss prior to bariatric surgery may reduce the risk of having blood clots in the veins, which is a leading cause of death after bariatric surgery," Dr. Bao said by email.

Patients with higher BMIs recorded shortly before surgery also had higher 30-day mortality, the study team reports in JAMA Network Open.

Compared to patients with a preoperative BMI of 35 to 39.9, patients with BMIs of 40 to 44.9 were 37% more likely to die within 30 days after surgery (OR 1.37). The risk steadily increased with rising BMI, and was roughly quintupled (OR 5.03) for patients with a BMI of 55 or higher.

Researchers also looked at patients' highest-ever recorded BMI at any point prior to surgery. Here, too, they found increasing mortality risk with rising BMI.

Compared to patients with a highest recorded BMI of 35 to 39.9, patients with a top BMI of 40 to 44.9 were 78% more likely to die within 30 days of surgery (OR 1.78). The risk was more than quintupled (OR 5.21) for with a highest recorded BMI of at least 55.

It's possible that individual hospital or surgeon characteristics might have impacted the outcomes in ways the study couldn't measure, the authors note.

The exact timing of weight measurements prior to surgery also isn't clear, and that could impact the outcomes for patients, said Dr. Dan Azagury, chief of minimally invasive and bariatric surgery at Stanford University School of Medicine in California.

"It could have been multiple days prior to surgery and patient could have lost more weight in the interim, confounding the data," Dr. Azagury, who wasn't involved in the study, said by email.

"The take-home message is that mortality risk is very low, and that losing weight prior to surgery is likely beneficial," Dr. Azagury said. "There is essentially no downside, and the modest weight loss noted here can be achieved over a couple of weeks just before the surgery."

SOURCE: and JAMA Network Open, online May 14, 2020.